In the related art, due to a reduction in the size of an electronic device or electric device, reductions in the size and the thickness of a component for electronic devices such as a terminal including a connector, a relay, and a lead frame used in the electronic device, the electric device, or the like have been achieved. Therefore, as a material of the component for electronic devices, a copper alloy having excellent spring property, strength, and electrical conductivity has been required. Particularly, as disclosed in Non-Patent Document 1, it is desirable that the copper alloy used in the component for electronic devices such as a terminal including a connector, a relay, and a lead frame has high proof stress and low Young's modulus.
As the copper alloy having excellent spring property, strength, and electrical conductivity, for example, a Cu—Ni—Si-based alloy (so-called Corson alloy) is provided in Patent Document 1. The Corson alloy is a precipitation hardening type alloy in which Ni2Si precipitates are dispersed, and has relatively high electrical conductivity, strength, and stress relaxation resistance. Therefore, the Corson alloy has been widely used in a terminal for a vehicle and a small terminal for signal, and has been actively developed in recent years.
In addition, as the other alloys, a Cu—Mg alloy described in Non-Patent Document 2, a Cu—Mg—Zn—B alloy described in Patent Document 2, and the like have been developed.
In the Cu—Mg based alloy, as is known from a Cu—Mg system phase diagram shown in FIG. 1, in a case where the Mg content is in a range of 3.3 at % or more, a solutionizing treatment (500° C. to 900° C.) and a precipitation treatment are performed so that intermetallic compounds including Cu and Mg can precipitate. That is, even in the Cu—Mg based alloy, relatively high electrical conductivity and strength can be achieved by precipitation hardening as is the case with the above-mentioned Corson alloy.